The relationship of the composition and structure of metalloenzymes to their function continues as the primary objective in the exploration of the physical and chemical basis of biological specificity proposed herein. Several well characterized metalloenzymes, including carboxypeptidase, thermolysin, alkaline phosphatase, alcohol dehydrogenase, and others are studied both to discern their mechanism of action as well as to provide general insight into the mode of interaction of metals with enzymes and proteins. Using these systems as models, new spectral and chemical probes are sought as tools for the study of structure and function of these proteins in solution. Concomitantly, utilizing new, highly sensitive spectroscopic techniques together with spectral and chemical probes, the separation and identification of metal-dependent components, particularly those containing zinc involved in both normal and abnormal growth and development, including neoplastic disease are being undertaken. Studies will be carried out with both microorganisms well as cultured human cells with the view toward establishing useful parallels with which to design further experiments in both systems. The participation of zinc, now firmly established, and other metals as well, in the mechanism of action of viral reverse transcriptases will continue to be explored in order to gain further insight into the mechanism of viral oncogenicity in animals.